[NTP::Push] Add Content Suggestions GCM App Handler

components/ntp_snippets/breaking_news/content_suggestions_gcm_app_handler.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/ntp_snippets/breaking_news/content_suggestions_gcm_app_handler.h"
+
+#include "base/strings/string_util.h"
+#include "components/gcm_driver/gcm_driver.h"
+#include "components/gcm_driver/gcm_profile_service.h"
+#include "components/gcm_driver/instance_id/instance_id.h"
+#include "components/gcm_driver/instance_id/instance_id_driver.h"
+#include "components/ntp_snippets/pref_names.h"
+
+using instance_id::InstanceID;
+
+namespace ntp_snippets {
+
+const char kContentSuggestionsGCMAppID[] = "com.google.contentsuggestions.gcm";
+
+// The sender ID is used in the registration process.
+// See: https://developers.google.com/cloud-messaging/gcm#senderid
+const char kContentSuggestionsGCMSenderId[] = "128223710667";
+
+// OAuth2 Scope passed to getToken to obtain GCM registration tokens.
+// Must match Java GoogleCloudMessaging.INSTANCE_ID_SCOPE.
+const char kGCMScope[] = "GCM";
+
+ContentSuggestionsGCMAppHandler::ContentSuggestionsGCMAppHandler(
+    gcm::GCMDriver* gcm_driver,
+    instance_id::InstanceIDDriver* instance_id_driver,
+    PrefService* pref_service,
+    std::unique_ptr<SubscriptionManager> subscription_manager)
+    : gcm_driver_(gcm_driver),
+      instance_id_driver_(instance_id_driver),
+      pref_service_(pref_service),
+      subscription_manager_(std::move(subscription_manager)),
+      weak_factory_(this) {}
+
+ContentSuggestionsGCMAppHandler::~ContentSuggestionsGCMAppHandler() {
+  StopListening();
+}
+
+void ContentSuggestionsGCMAppHandler::StartListening() {
+#if !defined(OS_ANDROID)
+  NOTREACHED()
+      << "The ContentSuggestionsGCMAppHandler should only be used on Android.";
+#endif
+  Subscribe();

[jkrcal, 2017/06/09 09:10:10]

For the sake of symmetry, maybe add something like the following?
DCHECK_EQ(gcm_driver_->GetAppHandler(kContentSuggestionsGCMAppID), nullptr);

[mamir, 2017/06/09 13:52:58]

This has been discussed before in this CL
tl;dr; AddAppHanlder already DCHECKs.

https://codereview.chromium.org/2922543002/diff/20001/components/ntp_snippets...

+  gcm_driver_->AddAppHandler(kContentSuggestionsGCMAppID, this);
+}
+
+void ContentSuggestionsGCMAppHandler::StopListening() {
+  DCHECK_EQ(gcm_driver_->GetAppHandler(kContentSuggestionsGCMAppID), this);
+  gcm_driver_->RemoveAppHandler(kContentSuggestionsGCMAppID);
+  std::string token = pref_service_->GetString(
+      ntp_snippets::prefs::kContentSuggestionsGCMSubscriptionTokenCache);
+  subscription_manager_->Unsubscribe(token);
+}
+
+void ContentSuggestionsGCMAppHandler::Subscribe() {
+  std::string token = pref_service_->GetString(
+      ntp_snippets::prefs::kContentSuggestionsGCMSubscriptionTokenCache);
+  if (!token.empty()) {
+    return;

[jkrcal, 2017/06/09 09:10:09]

I am puzzled by the assymetry in the code.

When you subscribe for the first time, you get a token and store it in prefs. If
you then unsubscribe, subscription_manager is called but the pref is not
cleared. Thus, when you re-subscribe later, subscription_manager does not get
called because the token in prefs is not empty.

[mamir, 2017/06/09 13:52:58]

Thank you for spotting this. You are absolutely right. This piece of code didn't
live here before. When I moved it, I forgot the adjust the rest of the flow
accordingly.

+  }
+
+  instance_id_driver_->GetInstanceID(kContentSuggestionsGCMAppID)
+      ->GetToken(kContentSuggestionsGCMSenderId, kGCMScope,
+                 std::map<std::string, std::string>() /* options */,
+                 base::Bind(&ContentSuggestionsGCMAppHandler::DidSubscribe,
+                            weak_factory_.GetWeakPtr()));
+}
+
+void ContentSuggestionsGCMAppHandler::DidSubscribe(
+    const std::string& subscription_id,
+    InstanceID::Result result) {
+  switch (result) {
+    case InstanceID::SUCCESS:
+      pref_service_->SetString(
+          ntp_snippets::prefs::kContentSuggestionsGCMSubscriptionTokenCache,
+          subscription_id);
+      subscription_manager_->Subscribe(subscription_id);
+      return;
+    case InstanceID::INVALID_PARAMETER:
+    case InstanceID::DISABLED:
+    case InstanceID::ASYNC_OPERATION_PENDING:
+    case InstanceID::SERVER_ERROR:
+    case InstanceID::UNKNOWN_ERROR:
+      DLOG(WARNING)
+          << "Push messaging subscription failed; InstanceID::Result = "
+          << result;
+      break;
+    case InstanceID::NETWORK_ERROR:
+      break;
+  }
+}
+
+void ContentSuggestionsGCMAppHandler::ShutdownHandler() {}
+
+void ContentSuggestionsGCMAppHandler::OnStoreReset() {
+  pref_service_->ClearPref(
+      ntp_snippets::prefs::kContentSuggestionsGCMSubscriptionTokenCache);
+}
+
+void ContentSuggestionsGCMAppHandler::OnMessage(
+    const std::string& app_id,
+    const gcm::IncomingMessage& message) {
+  // TODO(mamir): Implement Show notification and update the feed.
+}
+
+void ContentSuggestionsGCMAppHandler::OnMessagesDeleted(
+    const std::string& app_id) {
+  // Messages don't get deleted.
+  NOTREACHED() << "ContentSuggestionsGCMAppHandler messages don't get deleted.";
+}
+
+void ContentSuggestionsGCMAppHandler::OnSendError(
+    const std::string& app_id,
+    const gcm::GCMClient::SendErrorDetails& details) {
+  // Should never be called because we don't send GCM messages to
+  // the server.
+  NOTREACHED() << "ContentSuggestionsGCMAppHandler doesn't send GCM messages.";
+}
+
+void ContentSuggestionsGCMAppHandler::OnSendAcknowledged(
+    const std::string& app_id,
+    const std::string& message_id) {
+  // Should never be called because we don't send GCM messages to
+  // the server.
+  NOTREACHED() << "ContentSuggestionsGCMAppHandler doesn't send GCM messages.";
+}
+
+void ContentSuggestionsGCMAppHandler::RegisterProfilePrefs(
+    PrefRegistrySimple* registry) {
+  registry->RegisterStringPref(
+      prefs::kContentSuggestionsGCMSubscriptionTokenCache, std::string());
+}
+
+}  // namespace ntp_snippets